A Jealous killer murdered his partner after accusing her of having an affair with one of his sons.

Colin Kennedy, 63, was guilty of the "malevolent butchery" of Catherine Stewart at their home in Airdrie on July 4 2021.

One of their daughters came downstairs to find him carrying out the savage attack on the cancer survivor that Sunday morning.

Kennedy had become convinced the 54-year-old had been cheating on him with Colin Llewellyn - a son from a previous relationship.

He had earlier warned that he was going to "kill" his partner of 35 years before he struck.

Kennedy, of Kirkliston, Edinburgh, had claimed he was mentally ill at the time.

But, he was today found guilty of a murder that prosecutors said was "driven by anger and rage".

First offender Kennedy was jailed for life at the High Court in Glasgow and ordered to serve a minimum 25 years behind bars.

Jurors heard how the couple's relationship had deteriorated in the run-up to the killing.

Rows became common and they often sat in different rooms at their home.

Kennedy - nicknamed Coddy - had a total of seven children including two daughters and a son with Catherine.

He latterly had the "unshakeable" view his partner was seeing her step-son Colin Llewellyn, 45 - who stayed in Liverpool - behind his back.

This included him making a "secret clandestine recording" of a phone call between the pair.

This was played during the trial. At one stage, Catherine stated: "He is accusing me of something I have not done."

The grandmother instead claimed it was Kennedy who was previously guilty of infidelity.

Kennedy later met their son - also Colin - and told him: "I am going to kill your mum."

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On the morning of the attack, the couple's youngest daughter was upstairs when she heard Catherine shouting" Get off me".

The daughter- aged 17 at the time - told police: "I went into the kitchen and saw my mum lying on the floor in a pool of blood.

"I saw my dad stab my mum with a knife. I shouted at him to stop and tried to pull him off."

She recalled being in "full on panic mode" adding: "I was shaking. I was shocked - I could not even cry."

The slightly-built teenager grabbed at Kennedy as he continued the attack.

She also told police: "The only thing I thought of was 'I am going to lose my mum' and it is all my dad's fault."

The detectives praised the teenager for bravely trying to prevent what happened.

Kennedy was soon arrested - he confessed that he had stabbed Catherine and "just kept hitting her".

At the trial, he did not deny the killing, but had lodged a special defence of diminished responsibility.

Family members had concerns about him before Catherine's death mainly about his claims about the affair.

But, in his closing speech, prosecutor John McElroy KC said Kennedy was guilty of a "pre-meditated" killing.

He told jurors: "The Crown position is that this was murder, plain and simple.

"It was driven by anger and rage. His life, as he knew it, was coming to an end.

"He was suffering from stress, his partner wanted him out. The relationship had effectively come to an end.

"He was a jealous, angry and unhappy man."

Catherine was said to have made a comment to him that morning and Mr McElroy said Kennedy "lost his temper and stabbed her to death".

He initially knifed her in the back and then repeatedly in the chest.

Sentencing, Lord Arthurson told Kennedy: "This was not just a sustained episode of frenzied, instrumental violence.

"This was a cowardly attack of malevolent and wholly murderous butchery perpetrated on your partner."